1. Field of Invention
The present invention relates to cables including fillers.
2. Discussion of Related Art
It is common for electrical and optical cables to include a filler or multiple fillers. Fillers typically comprise string or extruded plastic components which occupy space within the cable. They may be provided to enhance the overall shape of and/or positioning of other components, for example conductors or optical fibers, relative to each other within the cable, or to provide mechanical protection. For example, a central filler may be surrounded by cable components, or interstitial fillers may be provided between cable components to give a cable a substantially circular cross section.
Where a cable is terminated, for example in a connecting device, the filler is normally redundant or superfluous. In many cases, the filler is of nuisance value to the installer who has to perform what is perceived as the extra task of removing it prior to terminating the cable. In some cable and connector designs where space limitation, connection procedures, or specific performance requirements dictate, the task can be difficult to achieve satisfactory and/or safely.
The problem of filler removal is particularly acute with the type of cables used for high speed data transmission. One design of cable employs four pairs of twisted insulated copper wires surrounding an extruded plastic filler element of cross-shaped cross-section. The filler serves to separate the twisted pairs to reduce the amount of signal interference (“crosstalk”) between them. Crosstalk is also reduced by careful selection of a different twist pitch for each element. The twisted pairs and filler are surrounded by an outer sheath.
Such cable is typically terminated in small connectors such as the industry standard RJ45-type. Making an interface between cable and connector requires great care by the installer to ensure that components combine in an effective manner to give a high performance connection. To achieve this some of the cable sheath must be removed to expose the wires, and the filler removed to the point of the cable sheath so that it does not interfere with the termination procedure or quality. To achieve this, the twisted pairs need to be displaced or folded back so that the filler can be cut.
This procedure has two major drawbacks. Firstly, the construction of the twisted pair is extremely precise in all respects. Disturbing the integrity of the twisted pair by displacement, bending, untwisting or other mechanical disturbance, may reduce cable performance significantly and irreparably. Secondly, installation engineers wish to minimize the number of steps and the time involved in each termination, and removal of such components can be awkward, time consuming and therefore costly.